植被格局对砒砂岩坡地降雨侵蚀的影响

Effects of vegetation pattern on rainfall erosion on Pisha sandstone slope land

为进一步研究砒砂岩区不同雨型下植被格局对坡面土壤侵蚀特征的影响,基于野外径流小区原位观测试验与景观生态学相结合的方法,通过对比分析不同坡面的植被斑块格局指数与产流产沙之间的相关关系,阐明植被格局对砒砂岩坡地降雨侵蚀的影响。结果表明:(1)该地区降雨可划分为3类,根据各植被坡面产流产沙能力,得出降雨侵蚀力表现为:雨型II(长历时、大雨量、大雨强)>雨型III(短历时、小雨量、中雨强)>雨型I(中历时、中雨量、小雨强)。降雨量和最大30min雨强与产流产沙量呈显著或极显著关系,相关系数0.695以上,是预测该区域水土流失的主要降雨因子。(2)各坡面水土保持能力与降雨类型有关,不同雨型下3种植被坡面减流减沙率分别达0.42%、20.8%以上,不同植被格局坡面减沙效益优于减流效益,3种植被坡面的减流能力为:雨型I>雨型III>雨型II。(3)3种植被坡面的径流泥沙模数由小到大依次为:均匀分布<聚集分布<随机分布,对比区域多年平均径流泥沙模数,3种植被坡面能够减少侵蚀达21.33%以上。(4)景观形状指数和分离度指数是影响坡面产流产沙的主要格局因子,相关系数分别达0.884和0.825以上。产流、产沙量与坡面植被斑块分离度呈显著正相关,与景观形状指数呈显著负相关。坡面产流量(Y_1)与斑块分离度(SPLIT)和景观形状指数(LSI)的关系式为Y_1=8.247SPLIT-6.605LSI+38.928,R~2=0.905。以上结果表明植被斑块间的分离度越小,形状越复杂,坡面阻力增大,抗侵蚀能力越强。研究成果可为生态恢复过程中植被斑块格局的优化提供理论依据和数据支撑。

In order to study the influence of vegetation pattern on slope soil erosion characteristics under different rainfall patterns in Pisha sandstone area,the erosion and sediment yield processes of uniform distribution,random distribution,aggregation distribution,and bare slope were studied by field runoff plot in⁃situ observation experiment.Combined with landscape ecology method,the pattern index of different vegetation patches was calculated,and the relationship between vegetation patch pattern and slope runoff and sediment yield was clarified.The results show that:(1)The rainfall in this area could be divided into three categories.According to the runoff and sediment yield capacity of each vegetation slope,the rainfall erosivity was as follows:rain type II(long duration,heavy rainfall,heavy rainfall intensity)>rain type III(short duration,small rainfall,medium rainfall intensity)>rain type I(medium duration,medium rainfall,small rainfall intensity).There was significant or extremely significant relationship between rainfall and the maximum 30 min rainfall intensity and runoff and sediment yield,and the correlation coefficient was more than 0.695,which was the main rainfall factor to predict soil and water loss in this area.(2)The soil and water conservation capacity of each slope was related to the type of rainfall.Under different rainfall patterns,the runoff and sediment reduction rates of the three vegetation slopes were more than 0.42%and 20.8%,respectively,and the sediment reduction benefits of different vegetation patterns were better than the runoff reduction benefits.The flow reduction capacity of the three vegetation slopes was:rain type I>rain type III>rain type II.(3)The runoff and sediment modulus of the three vegetation slopes from small to large was:uniform distribution<aggregation distribution<random distribution.Compared with the average runoff and sediment modulus of the region for many years,the three vegetation slopes could reduce erosion by more than 21.33%.(4)The landscape shape index and the separation index were the main pattern factors affecting the runoff and sediment yield on the slope,and the correlation coefficients were above 0.884 and 0.825,respectively.The runoff and sediment yield were significantly positively correlated with the separation degree of vegetation patches on the slope,and negatively correlated with the landscape shape index.The relationship between slope runoff yield(Y1)and patch separation index(SPLIT)and landscape shape index(LSI)was Y1=8.247SPLIT-6.605LSI+38.928,R2:0.905.The above results show that the smaller the separation between vegetation patches,the more complex the shape,the greater the slope resistance,and the stronger the erosion resistance.The research results can provide theoretical basis and data support for the optimization of vegetation patch pattern in the process of ecological restoration.